Interferons are a group of natural proteins that occur in the cell division process and exhibit anti-viral, antitumor, and immunomodulatory activities. The recombinant human interferon α and interferon β have been used as drugs for treatment of viral infections, cancer and multiple sclerosis. In the treatment of both hepatitis C and hepatitis B, interferon ox is the only effective agent on the market, and has become the standard therapy. However, because of its short circulation half-life (4-8 hours), their anti-viral activity and long-term treatment effect are limited. Recently, Schering-Plough and Hoffmann-La Roche have independently developed long-lasting interferon a formulations by conjugating with a synthetic water-soluble polymer. In 2001, Schering's product, PEG-intron®, obtained approval from the US FDA for treatment of hepatitis C. Roche's product, Pegasys®, had finished clinical studies and is waiting for the US FDA's approval. In WO01/74399A1, a targeted system using galactose-PEG was disclosed. Although it can obtain the effect of targeting toward the suffered tissue for interferon, but the measures for applying it are very complicated and difficult to meet the industrial needs. In addition, the polymer cannot be conjugated with interferon in an aqueous phase, and the conjugation must be catalyzed with enzyme.
Polyethylene glycol has been widely used in the field of protein conjugation. The resulting conjugates will improve in vivo circulation half-lives, and reduce immunogenecity and toxicity for proteins, peptides and other therapeutics. In both PEG-intron® and Pegasys®, polyethylene glycol not only improves their anti-viral efficacy but also reduces their injection frequency from three times a week to once a week.
However, neither PEG-intron® nor Pegasys® can achieve greater than 60% patient sustained response rate. Especially for hepatitis C virus of genotype I, sustained response rate is lower than 42%. To further improve the efficacy of interferon, it is believed that targeted delivering more interferon to the virus infected tissues or organs could be very beneficial.
In the researches of glycobiology, many bio-macromolecules on the cell surface are glycosylated compounds, also referred to glycoconjugate. They can be further classified into three types: glycoproteins, protcoglycans and glycolipids. Glycosylated compounds with extending oligosaccharides are the typical components anchored on the surface of cell membrane, cell wall and organella. The extending sugar parts have functions of information coding, which play very important roles in cell-cell recognition. For example, the recognition between a sperm and an egg in reproduction process is modulated by the sugar-protein interactions.
Polysaccharides are not the direct products of gene transcription, but their biosynthesis is adjusted by post translation. When there is a defect in the cell adjusting mechanism (such as in auto-immune diseases, cancer or other gene-related diseases), sugar synthesis and degradation are altered, resulting in changes in the component and composition of the sugar on the cell surface, leading to the alternation of the whole immune system. Comparing to amino acids, nucleotides, and fatty acids, the structures of saccharides are more complicated. For example, two different amino acids can produce two kinds of dipeptides, while two monosaccharides can produce eleven kinds of disaccharides. Three amino acids can produce six kinds of tripeptides, while three monosaccharides can lead to 1,056 kinds of trisaccharides. It is due to the branching properties of saccharide structure, which differs polysaccharides from other bio-macromolecules (such as proteins and polynucleotides). Based on its inherent structural complication, polysaccharides have become the carriers of detailed biological information, playing an important role in cell recognition and signal transduction.
Liver cancer is one of the common malignant cancer. Very few patients can be treated with surgical removal, and at same time, chemical and radical therapies have very low response rate. In China, liver cancer results in 100,000 deaths every year, and becomes the leading death cause in some parts of China. The major aim of the present invention is to improve the efficacy and lasting effect of the medicines toward liver diseases.
The asialoglycoprotein receptor (ASGPR) is a trans-membrane glycoprotein only existing on the liver cells of mammals. ASGPR can specifically recognize and then binds with the glycoproteins having a galactose unit at the terminal. The formed ligand-receptor complex can then be internalized into lysosome, and the macromolecule can be release a ASGPR itself will not be degraded, but recycle back to the surface of the cell membrane to participate into next cycle of transportation. Because of its specific property, ASGPR is also called liver specific galactose (H-Gal) receptor.
It is believed that with the combination of targeting agent and hydrophilic polymer, the interferon level at the infected tissues and organs will be increased, which will improve the anti-virus effect and achieve an improved treatment efficacy. In the treatment of hepatitis C and B, the efficacy of interferon will be significantly increased by extending its circulation half-life with PEGs and redirecting its distribution in the body, especially in the liver by the targeting agents. As a result, it is expected that anti-viral efficacy for treatment of hepatitis C and hepatitis B will be increased.